Damping Of Bearings Research Articles

Study on seismic performance of functionally integrated cylindrical steel damper bearing with energy dissipation and spacing

The bridge bearing serves as a crucial constituent that can exert a substantial influence on the seismic performance of the bridge structure. When subjected to seismic events, conventional fixed-type bearings transmit considerable seismic forces, leading to detrimental effects on the bridge piers. The damage incurred by the fixed-type bearings can result in significant relative displacement between the pier and girder, which can potentially contribute to the unseating. To effectively control the seismic damage to bridge piers and the relative displacements between the pier and girder, as well as to facilitate controllable design of bridge seismic behaviors, a novel functional integration approach was developed: the functionally integrated cylindrical steel damper bearing (FICSDB). The FICSDB incorporated certain functionalities, such as seismic isolation, energy dissipation, and displacement limitation. Specifically, following the constructional details and operational mechanisms of the FICSDB, the mechanical model was initially derived. Subsequently a series of cyclic shear tests were conducted on the FICSDB. Certain results were obtained as follows. (1) The bearing’s sliding performance remained relatively stable. (2) The cylindrical damper effectively achieved the desired objectives of energy dissipation and spacing, thereby exhibiting exceptional fatigue resistance. (3) The components demonstrated close cooperation, which ensured the overall stability and controllability of the FICSDB’s mechanical behavior. (4) The effectiveness of the FICSDB was validated through numerical calculations with the application of a continuous girder bridge as a case study. The results revealed that, in comparison to traditional fixed-type bearings, employing the FICSDB significantly reduced internal forces exerted on the bridge piers during rare seismic events. Additionally, when compared to conventional isolation bearings, the FICSDB realized the excellent minimization of the relative displacement between the pier and girder. Therefore, the FICSDB can enable the dual control of the pier damage and unseating, thereby facilitating the controlled design of bridge seismic behaviors.

Experimentally Measured Effectiveness of Different Shroud Swirl Brake Profiles in a Centrifugal Compressor

Abstract As centrifugal compressors are pushed to operate at higher pressures and higher power levels, destabilizing gas forces often increase the challenge of designing a stable rotordynamic system. While technical innovations like damper seals, swirl brakes, and damper bearings that help stabilize compressors are numerous, predicting the impact that these improvements will have on a specific system is somewhat of an art form. To this end, researchers are constantly improving the depth of knowledge on these features so that the impact of these improvements is well defined. In the current work, the authors experimentally measured the impact of different swirl brake/vane concepts on the flow characteristics of a centrifugal compressor shroud cavity. The eye seal configuration studied here is a tooth on rotor labyrinth eye seal. The different shroud swirl vane geometries considered consist of various castellated features, each having the intent to reduce swirl velocity in the shroud cavity prior to entering the seal. The purpose of the testing was to determine whether a significant reduction in swirl velocity entering or exiting the seal could be measured with the different antiswirl vane profiles over a conventional shroud cavity that was tested with the same setup. The metrics that determine the effectiveness of the swirl brake were based on upstream and downstream measurements of swirl velocity using pitot-probes at different depths in the shroud cavity, and measurements of seal exit angle and velocity using a traversing cobra-probe. The test data presented herein show definitively that the different swirl brake designs, including a slotted seal, a long vane, and a short vane, have a major impact on swirl velocities relative to the conventional shroud design. The most effective at reducing swirl entering/leaving the seal is the slotted seal, while the concepts employing shroud vanes were more effective at reducing swirl in the shroud cavity.

Seismic Response and Economic Study of New Light Steel-Wood-Plastic Structure in Rural Yunnan, China

A new type of light steel-wood-plastic residential structure in rural has popular in recent years in rural Yunnan, China. The application of light steel, wood, and new plastic materials in practical engineering is gradually increasing due to its advantages of green ecology and waste utilization, and its response characteristics under earthquakes have attracted great attention. In this paper, seismic-resistant models, seismic-isolated models, and seismic-damped models for multistorey light steel-wood-plastic structures were established using the SAP2000 finite element software based on different seismic response methods. The seismic-isolated model is divided into five schemes, namely, LRB400, LRB500, LRB600, high damped, and friction pendulum-isolated bearings, and the seismic-damped model is divided into three schemes, namely, ordinary bracing, soft-steel bracing, and BRB bracing at the same locations around the 2nd floor of the building. Nonlinear time analysis was carried out for the nine schemes, comparing the period, structural interstorey displacement, base shear, top displacement, top acceleration, and economy of the structure under the action of an 8-degree earthquake. Results show that the period of the seismic-isolated system increased by approximately 130% compared to the seismic-resistant system, and the period of the damped system decreased slightly compared to the seismic system, the interstorey displacement, base shear, and top acceleration of both the seismic-isolated system and the damped system were smaller than those of the seismic-resistant system, and the seismic-isolated system decreased by approximately 40% compared to the damped system, and the seismic-isolated system was more effective than the damped system. From the comparison of postearthquake damage cost and full-cycle cost, the economic performance of the seismic-isolated structure is better than that of the damped and seismic-resistant structures. The conclusions of this paper can provide a scientific reference for promoting the use of new light steel-wood-plastic residential buildings.

A blockchain-based cooperative modeling method for digital twin ontology model of the mechanical product

With the rapid increase of multi-source heterogeneous dynamic data of mechanical products, the digital twin technology is considered to be an important method to realize the deep integration of product data and intelligent manufacturing. As a digital archive of the physical entity in entire life cycle, the mechanical product digital twin model is cross-phased and multi-domain. Therefore, safe and stable cooperative modeling has become a basic technical problem that needs to be solved urgently. In this paper, we proposed a blockchain-based collaborative modeling method for the digital twin ontology model of mechanical products. First, an authorization network was constructed among stakeholders. Then modeling processes of the digital twin were mapped to ontology operations and formatted through extensible markup language. Finally, consensuses were obtained based on practical byzantine fault tolerance. And a material modification process of a helicopter damper bearing was taken as an example to verify. The proposed method enables all participants to accurately obtain the latest state of the digital twin model, and has the advantages of tamper-proof, traceability, and decentralization.

Numerical Evaluation and High-Speed Rotating Test on Circular Arc Spring Dampers for Centrifugal Compressors

Abstract A circular arc spring damper (CASD) is a recently proposed fluid-film damper that has two or more arc-shaped centering springs and dual radial clearances formed by wire electric discharge machining (WEDM). CASD requires less space and weight than a conventional cage-centered squeeze-film damper (SFD). It provides linear stiffness and stable damping force in rotor-bearing systems to attenuate vibration due to imbalance or to improve rotordynamic stability. The authors have been investigated the dynamic characteristics of CASD in component-level experiments. However, their performance and applicability to real machines have not been confirmed in system-level experiments. Additionally, a theoretical means of evaluation for CASD should be established to predict its dynamic coefficients and to understand the mechanism of dynamic force generation. In the first part of this study, a numerical evaluation method using two-way fluid–structure interaction (FSI) analysis and its theoretical background is presented. Transient structural analysis and fluid-film flow analysis with a simple homogeneous cavitation model are coupled in the commercial multiphysics platform ansys. The accuracy of the method was validated by comparing the damping and added-mass coefficients with results from previous experiments. Furthermore, several aspects of the force generation mechanism and the difference from conventional SFD were studied numerically. The second part of the study addresses the application of CASD in a multistage centrifugal compressor. A combined 4-in. diameter, five-pad tilting pad journal bearing (TPJB) with four-arc type CASD was newly designed and manufactured. To prove the applicability of the developed damper bearing, a series of rotating tests were conducted at a high-speed balancing facility with a full-scale dummy rotor with a critical speed ratio (CSR) of approximately 3.1. The measured unbalance response showed a much lower amplification factor (AF) than that of the conventional TPJB without the damper, which infers a significant improvement in the stability. The measured responses agreed with the rotordynamic analysis, which uses the dynamic coefficients of CASD derived from the proposed numerical evaluation method.

Multi-Objective Optimization Design of a Novel Integral Squeeze Film Bearing Damper

In order to better control the vibration of the rotor system so as to improve the stability and safety of the rotor, a novel vibration control solution is needed. In this paper, the multi-objective optimization problem is used for designing a novel integral squeeze film bearing damper (ISFBD). The method attempts to reduce the stiffness and stress convergence of ISFBD, which can greatly decrease the transmitted force of the rotor system and better use the damping effect to dissipate the vibration energy. The finite element model of ISFBD is established to analyze the stiffness and stress, and the correctness of the calculation is verified by setting up a stiffness test platform. The sensitivity of different structural parameters of stiffness and stress is analyzed by ANOVA. Meanwhile, the non-dominated sorting genetic algorithm (NSGA-II) and grey correlation analysis (GRA) algorithms are coupled for multi-objective optimization of stiffness and stress. The results indicate that optimized ISFBD can distribute 26.6% of the rotor system’s energy and reduce 59.3% of the transmitted force at the bearing location. It is also proved that the optimization strategy is effective, which can provide a useful method for ISFBD design in practical applications.

Study on seismic performance of frame structure with viscous damping staircase

Based on the significant energy dissipation performance of the viscous damper, the force-displacement hysteresis curve is full and the Maxwell mechanical model has a weak dependence on vibration frequency. Combining the failure mode of the staircase damage with the Maxwell mechanical model, this paper proposes an earthquake-resistant frame staircase model with damped bearings. A finite element analysis of a nine-story reinforced concrete structure is performed using SAP2000. By setting three different connection methods on the staircase structure, the similarities and differences of different staircase structures to the input seismic wave feedback are analyzed to compare the advantages and disadvantages of its seismic performance.

DEVELOPMENT AND EXPERIMENTAL INVESTIGATION OF SELF-CENTERING DAMPERS WITH PARALLEL HIGH STRENGTH STEEL RING SPRING GROUPS

Based on the self-centering damper with high-strength steel ring spring, a self-centering damper with parallel high-strength steel ring spring is proposed. The seismic performance of the parallel ring spring self-centering damper under multiple seismic conditions was verified by a hysteretic test. The test results show that the parallel high-strength steel ring spring self-centering damper has good self-centering ability, and will not experience performance degradation after multi-time earthquakes. It does not need to be replaced after the earthquake. Compared with the self-centering damper with a single group of ring springs, the damper bearing capacity can be effectively improved under the same size, and the damper internal space can be fully utilized. The different frictional conditions of the annular spring contact surface have a certain influence on the performance of the self-centering damper. The theoretical prediction model proposed is in a good agreement with the experimental results.

Increasing the Life of the Slider Bearings of the Turbines of High-Speed Compressors

Problems that arise in the operation of modernized compressor turbines related to the increase in the temperature of the support part of a combined journal and axial bearing of the 103JT turbine are considered. The increase in temperature reduces the bearing and damping ability of the slider bearing and is accompanied by subsidence of the rotor. One effective solution to the problem may involve replacement of the standard bearings by TRIZ damper bearings, by means of which the support capacity of the bearings may be increased, friction-induced power losses reduced by 22%, the maximum temperature of the pads decreased by 13%; the surface of the pads protected against electro-erosion damage; the problem of rotor subsidence successfully solved, and the bearing life increased without changing the pads.

Vibration Control of an Unbalanced Single-Side Cantilevered Rotor System with a Novel Integral Squeeze Film Bearing Damper

In this paper, vibration control of an unbalanced single-side cantilevered rotor system using a novel integral squeeze film bearing damper in terms of stability, energy distribution, and vibration control is analyzed. A finite element model of such a system with an integral squeeze film bearing damper (ISFBD) is developed. The stability, energy distribution, and vibration control of the unbalanced single-side cantilevered rotor system are calculated and analyzed based on the finite element model. The stiffness of the integral squeeze film bearing damper is designed using theoretical calculation and finite element model (FEM) simulation. The influence of installation position and quantity of integral squeeze film bearing dampers on the vibration control of the unbalanced cantilevered rotor system is discussed. An experimental platform is developed to validate the vibration control effect. The results show that the installation position and quantity of the integral squeeze film bearing dampers have different effects on the stability, energy distribution, and vibration control of the unbalanced cantilevered rotor system. When ISFBDs are installed at both bearing housings, the vibration control is best, and the vibration components of the time and frequency domains have good vibration control effects in four working conditions.

An insight into the dynamics of a rigid rotor on two-lobe wave squeeze film damper

Differently from journal bearings and to author's knowledge, the adoption of lobe geometry in the bearing bore of squeeze film dampers (SFD) has not received any research interest, except for some recent study due to the present author. In this study, a relatively simple system, represented by a rigid, unbalanced rotor on two-lobe SFD, is theoretically investigated by means of numerical continuation. Despite being restricted to periodic solutions, this numerical procedure permits an efficient characterization of the system's bifurcating behaviour, suitably taking into account the shape parameters of the wave profile given to the bore of lobed damper bearing. In particular, the influence of the bearing angular position on the synchronous (1-S) and order-two subharmonic solutions (1/2-S) has been analyzed, assuming the rotor speed as the bifurcation parameter, under different conditions of bearing operation that are expressed by means of the bearing parameter f. The results are compared to the corresponding behaviour of the rotor on dampers with circular bearing (CB). The bifurcation structure shows to be rather influenced by both the angular position and f. With regard to the 1-S, the two-lobe geometry emphasizes some effects obtained raising f in the presence of CB. Some other effects show to be distinctive features of the lobed geometry, like the disappearance of the torus bifurcation and the length modification (as increase or decrease) of the segments representing unstable behaviour. A significant simplification in the bifurcation paths of the 1/2-S, as compared to the CB set-up, is achieved at higher f values, especially through suitable angular positions. Contrast with this outcome the relatively involved path-patterns obtained for the sub-harmonic responses at the lowest f value. The study represents an insight with respect to the author's previous works on this subject, which were mainly focused on the characterization of the synchronous behaviour.

Influence of the Radial Clearance of a Squeeze Film Damper on the Vibratory Behavior of a Single Spool Gas Turbine Designed for Unmanned Aerial Vehicle Applications

This study presents a numerical investigation using the finite element method on the vibratory behavior of a single spool gas turbine designed for unmanned aerial vehicle applications. The shaft of the rotor-bearing system is supported on a front bearing composed of a deep groove ball bearing with a vibration absorber element and a rear squeeze film damper bearing. Three radial clearances for the squeeze film damper were analyzed to determine the best geometric configuration for the rear bearing, considering the rotordynamic performance of the entire system. Whirl speeds and unbalanced system responses were carefully evaluated to determine the best radial clearance for the squeeze film damper. After defining the best radial clearance, a transient analysis was performed to simulate the transition of the system through resonance, and a spectral map is presented to illustrate the vibratory behavior of the system considering the influence of all related important frequencies. The rotordynamic behavior of the system is predicted, and vibration problems are avoided. Its mechanical drawings were released to manufacturing, and the first prototype is in the experimental test phase, thus indicating that the numerical results presented in this study are consistent.

Empirical identification of the inverse model of a squeeze-film damper bearing using neural networks and its application to a nonlinear inverse problem

The identification of nonlinear squeeze-film damper (SFD) bearings, typically used in aero-engines, has so far focused on their forward model (i.e. displacement input/force output). The contributions of this paper are the non-parametric identification of the inverse model of the SFD bearing (force input/displacement output) from empirical data, and its application to a nonlinear inverse rotor-bearing problem. This work is motivated by the need for a reliable substitute for internal instrumentation, to enable the identification of rotor unbalance using vibration data from externally mounted sensors, in applications where the rotor is inaccessible under operating conditions and there is no adequate linear connection between rotor and casing. The identification of the inverse model is fundamentally different from that of the forward model due to the need to account for system memory. A suitably trained Recurrent Neural network (RNN) is shown to be capable of identifying the inverse model of an actual SFD through two validation studies. In the first study, the RNN model satisfactorily predicted the SFD journal’s displacement time histories for given periodic time histories of the Cartesian SFD forces, although it could not predict the user-applied static offset in the SFD since it was not trained to do so. This was no limitation for the second study where, for both centred and non-centred SFD conditions, the RNN proved to be a reliable substitute for actual instrumentation as part of the inverse problem solution process for identifying the amplitudes and phases of the external excitation forces on a simple test rig.

A theoretical and experimental investigation of the dynamic response of a squeeze-film damped twin-shaft test rig

This article performs a theoretical and experimental analysis of a twin-shaft test rig in which the two unbalanced rotors are nonlinearly coupled through the flexibly mounted housing of a squeeze-film damper bearing, as in a real aircraft engine. The research aims are two-fold: to validate recently developed fast computation methods and to achieve an insight into the effect of the ratio between the rotor speeds on the overall vibration response. The experimental data correlated reasonably well with the theoretical analysis. The correlation was best when the speed ratio was equal to a ratio of large integers (in its most reduced form). When the speed ratio was a ratio of two low integers, the predicted response was found to be particularly sensitive to the arbitrary initial phase angle between the rotors.

Empirical identification of squeeze-film damper bearings using neural networks

To date empirically obtained SFD models have been based upon the determination of linearised force coefficients; such models are severely limited in their range of applicability since they are only valid for small perturbations from a mean position. The present research provides the introduction and validation of a nonlinear SFD identification technique that uses neural networks, trained from experimental data, to reproduce the input–output function over the full range of the SFD clearance. Details of the commissioning of a specially designed identification test rig and its associated data acquisition system are presented. The neural network's construction and training process is described and relevant testing is detailed. The empirically identified neural network is progressively validated, culminating in remarkably accurate nonlinear vibration response prediction of an SFD test rig subjected to external dual-frequency orthogonal excitation, as present in twin-spool engines (where the nonlinear vibrations are driven by the unbalance on the two rotors turning at different speeds). When used within the dynamic analysis of the test rig, the trained neural network is shown to be capable of predicting complex nonlinear phenomena with excellent accuracy. By comparison to an advanced theoretical model, the results show that the neural networks are able to capture the effects of features that are difficult to include in a hydrodynamic model or are particular to a given SFD.

Non-linear dynamic analysis of hybrid squeeze-film damper-mounted gear-bearing system and hydraulic active control

The hybrid squeeze-film damper bearing is proposed in this article. The pressure distribution and the dynamics of a gear pair supported by such bearing are studied. Numerical results show that, due to the non-linear factors of lubricant film force, the trajectory of the gear demonstrates a complex dynamics with rotational speed ratio s. Poincaré maps, and bifurcation diagrams are used to analyse the behaviour of the gear trajectory in the horizontal and vertical directions at s = 6.0. The maximum Lyapunov exponent is used to determine if the system is in a state of chaotic motion. Numerical results show that the maximum Lyapunov exponent of this system is positive at the non-dimensional speed ratio s = 6.0, which indicate that the gear trajectory is chaotic under such operation condition. In order to avoid the non-synchronous chaotic vibrations, an increased proportional gain k p = 0.1 is applied to control this system. It is shown that the gear trajectory leaves chaotic motion to periodic motion in the steady state under control action.

Design and Evaluation of Damped Air Bearings at Head-Disk Interface

Perturbation and modal-analysis methods were employed to systematically study a damped slider’s dynamic characteristics, including an air-bearing slider’s stiffness, damping coefficient, frequency response to translation and wavy motion, natural frequencies, damping ratios, and modal shape-node line. We found that a design with grooves distributed on a trailing pad effectively improved the slider’s damping ratio in the second pitch mode; however, parametric studies revealed that the damping ratio was dependent on the number of grooves, their depth, location, width, length, distribution, orientation, and types. A higher damping ratio could be obtained by optimizing these parameters. The femto slider we designed with distributed damped grooves on a trailing pad had a higher damping ratio in the second pitch mode, and hence, its responses in the second pitch mode were greatly reduced, which were clarified through simulation and an experiment. Some issues on air-bearing stiffness reduction and negative damping at low frequency and contamination and lube pickup on the damped grooves were also evaluated in the experiment. No degradation could be found in the damped slider.

Computational Studies of the Unbalance Response of a Whole Aero-Engine Model With Squeeze-Film Bearings

The computation of the unbalance vibration response of aero-engine assemblies fitted with nonlinear bearings requires the retention of a very large number of modes for reliable results. This renders most previously proposed nonlinear solvers unsuitable for this application. This paper presents three methods for the efficient solution of the problem. The first method is the recently developed impulsive receptance method (IRM). The second method is a reformulation of the Newmark-beta method. In addition to these two time-domain methods, a whole-engine receptance harmonic balance method (RHBM) is introduced that allows, for the first time, the frequency domain calculation of the periodic vibration response of a real engine. All three methods use modal data calculated from a one-off analysis of the linear part of the engine at zero speed. Simulations on a realistically-sized representative twin-spool engine model with squeeze-film damper bearings provide evidence that the popular Newmark-beta method can be unreliable for large-order nonlinear systems. The excellent correlation between the IRM and RHBM results demonstrates the efficacy of these two complementary tools in the computational analysis of realistic whole-engine models.

An impulsive receptance technique for the time domain computation of the vibration of a whole aero-engine model with nonlinear bearings

The direct study of the vibration of real engine structures with nonlinear bearings, particularly aero-engines, has been severely limited by the fact that current nonlinear computational techniques are not well-suited for complex large-order systems. This paper introduces a novel implicit “impulsive receptance method” (IRM) for the time domain analysis of such structures. The IRM's computational efficiency is largely immune to the number of modes used and dependent only on the number of nonlinear elements. This means that, apart from retaining numerical accuracy, a much more physically accurate solution is achievable within a short timeframe. Simulation tests on a realistically sized representative twin-spool aero-engine showed that the new method was around 40 times faster than a conventional implicit integration scheme. Preliminary results for a given rotor unbalance distribution revealed the varying degree of journal lift, orbit size and shape at the example engine's squeeze-film damper bearings, and the effect of end-sealing at these bearings.

Seismic Shock Absorber for Arab Highway

In the United Arab Emirates, infrastructure must be able to withstand earthquakes. Trelleborg's damped bearings are used to secure a six-lane expressway bridge.